Bill.Satellite your statement "It is so unlikely that the problem is the "disk" that I would simply discount that option" is inaccurate and not helpful to the OP. Don't know your experience but I've found several accounts of such problems here in various forums and personally know of three, not including my own. Additionally, when I talked to the factory that built out coach the service representative stated that it does occasionally happen. The cutout blank simply falls off the hole saw and drops into the tank when it is removed. My method of determining if that is the case is valid and recommended by the manufacturer. Sorry to bust your bubble.
